This invention pertains to structures for holding disks during sputtering. This invention also pertains to methods and apparatuses for manufacturing magnetic disks.
Magnetic disks are typically manufactured by sputtering an underlayer, a magnetic alloy film and a protective overcoat, in that order, on a disk-shaped substrate. An example of such a process is described in U.S. patent application Ser. No. 08/984,753, filed by Bertero et al. on Dec. 4, 1997 (now U.S. Pat. No. 6,150,015, issued Nov. 21, 2000), incorporated herein by reference.
During sputtering, the following steps are typically performed:
1. A disk-shaped substrate is placed in a xe2x80x9cdisk carrierxe2x80x9d. (The substrate can be glass, glass ceramic, aluminum plated with a nickel-phosphorus alloy, or other appropriate material. The nickel-phosphorus alloy is sometimes referred to as xe2x80x9cNiPxe2x80x9d.)
2. In some (but not all) manufacturing processes, the disk carrier carries the substrate past a heating element for heating the substrate.
3. The disk carrier carries the substrate through sputtering apparatus, past several sets of sputtering targets.
4. The substrates are then removed from the disk carrier.
Various types of disk carriers are known in the art. For examples of disk carriers used during low temperature sputtering processes see U.S. Pat. Nos. 5,244,555; 5,296,118; and 4,595,481, each assigned to Komag, Inc. and incorporated herein by reference. These disk carriers include a vertical plate with a substantially circular opening for receiving a disk-shaped substrate. A groove is provided in the bottom of the circular opening for receiving and holding the outer edge of the substrate. During low temperature sputtering processes, the substrate is placed within the carrier and carried past a set of sputtering targets. The substrate is typically not carried past a heating element prior to sputtering. Therefore, the carrier need not accommodate much thermal expansion of the substrate relative to the carrier.
U.S. patent application Ser. No. 09/428,301, filed Oct. 27, 1999 abandoned and assigned to Komag, Inc., teaches and claims several types of disk carriers used in a high temperature sputtering process. (The ""301 application, which is now abandoned, is incorporated herein by reference.) The ""301 carriers also include a vertical plate with a circular opening for receiving a substrate. For example, in ""301 FIGS. 2A to 2E (FIGS. 1A to 1E of the present application), the ""301 application shows an embodiment of a disk carrier 100 comprising a vertical plate 102 having a substantially circular opening 104 for receiving a disk-shaped substrate 106. During a high temperature sputtering process, carrier 100 carries substrate 106 past a heating element prior to sputtering. Because substrate 106 has a much lower thermal mass than carrier 100, the temperature of substrate 106 can exceed the temperature of carrier 100 by 200xc2x0 C. or more. Accordingly, carrier 100 has the following characteristics.
1. Opening 104 has a size and shape such that it can hold substrate 106 when substrate 106 and carrier 100 are both at room temperature.
2. Opening 104 can hold substrate 106 when substrate 106 is at an elevated temperature with respect to carrier 100 without having carrier 100 pressing against substrate 106 so as to cause substrate 106 to bend or bow.
Substrate 106 is disk-shaped and has a diameter of 95.025 mm (e.g. a radius of about 47.513 mm) at room temperature, a thickness of 0.80 mm at room temperature, a diameter of 95.572 mm at 300xc2x0 C. and a thickness of 0.890 at 300xc2x0 C. Substrate 106 has a central aperture 107 formed therein. Substrate 106 typically comprises an aluminum alloy plated with a NiP.
Opening 104 of carrier 100 comprises an upper circular portion 104u and a lower circular portion 104l. Upper circular portion 104u has a radius R1 equal to about 48.82 mm about a center C. (Radius R1 is greater than the room temperature substrate radius.)
Lower portion 104l of opening 104 extends about an arc of approximately 176xc2x0. Within lower circular portion 104l is a groove 108 (FIGS. 1C to 1E) for receiving an outer edge 106a of substrate 106. Groove 108 extends continuously along the length of circular portion 104l. Groove 108 includes side walls 108a, 108b (FIG. 1E) which form an angle xcex1l of about 100xc2x0 and a floor 108c having a width W1 of about 0.25 mm. The distance D1 (FIG. 1A) between the center C of opening 104 and the top 108t of groove 108 is typically between 47.424 and 47.454 mm (i.e. less than the substrate radius). The distance between the center C of opening 104 and floor 108c of groove 108 is typically between 47.907 and 47.937 mm (i.e. greater than the substrate radius). Groove 108 terminates when it reaches points 109a, 109b (FIG. 1A). Points 109a, 109b are about 2xc2x0 below the horizontal diameter of opening 104.
At room temperature substrate 106 has a radius of 47.513 mm and a thickness of 0.800 mm. Thus, when substrate 106 is at room temperature and rests in groove 108, edge 106a of substrate 106 is a distance D2 of about 0.12 mm from floor 108c of groove 108 (FIG. 1Exe2x80x2). At a substrate temperature of 300xc2x0 C., edge 106a is about 0.16 mm from floor 108c. Substrate 106 is adequately supported by groove 108 when substrate 106 is at room temperature (about 20xc2x0 C.). However, because the radius of floor 108c of groove 108 is greater than the substrate radius at room temperature, carrier 100 can accommodate thermal expansion of substrate 106 without causing substrate 106 to bow outwardly. During some high temperature processes, substrate 106 is heated to a temperature of about 200xc2x0 C. before sputtering.
Above points 109a, 109b, groove 108 terminates, and a recess 112 having a depth D4 of about 6.35 mm (FIG. 1D) is formed in a side 114 of carrier 100. (Carrier 100 has a width D5 of about 11 mm.) The walls of recess 112 include first and second portions 112a, 112b (FIG. 1A) which extend in a linear direction, and a third, curved portion 112c. Recess 112 permits loading and removal of substrate 106 from side 114 of carrier 100. (However, it is not feasible to load substrate 106 from the other side 117 of carrier 100.) Curved portion 112c of the wall of recess 112 is circular, and has a radius R2 of about 53.80 mm from a point Cxe2x80x2 that is a distance D3 about 4.44 mm above center point C. Linear walls 112a and 112b are a distance D4 of about 52.10 mm from point Cxe2x80x2.
A bevel 116 is formed on side 114 of carrier 100 to facilitate exposure of substrate 106 to plasma during sputtering. Similarly, a bevel 118 is formed on side 117 of carrier 100, also to facilitate exposure of plasma to substrate 106 during sputtering. Bevels 116 and 118 form an angle xcex31 of 26xc2x0 (FIG. 1E) with the side of carrier 100. Bevels 116 and 118 are circular, with a radius R3 of about 57.16 mm from center C (FIG. 1A).
FIG. 1C is an expanded view of a portion P1 of FIG. 1A where groove 108 terminates. As can be seen, below wall 112a, a wall 112d that curves downward and to the right toward opening 104 bounds recess 112. The radius of curvature R4 of wall 112 is about 4 mm.
The ""301 application teaches and claims several other types of substrate carriers, e.g. as shown in ""301 FIGS. 3A to 3C and 4A to 4D. The embodiment of ""301 FIGS. 3A to 3C permits a substrate to be loaded and unloaded from either side of the disk carrier. The embodiment of ""301 FIGS. 4A to 4D has a groove that is shallower at the lowest point of the opening (e.g. near point 109c) than away from the lowest point of the opening (e.g. near points 109a, 109b). This makes it easier for the carrier to hold the substrate when the substrate is at room temperature without having the substrate fall out of the opening. As mentioned above, the ""301 application is incorporated herein by reference.
Magnetic disks come in standard sizes. One of the most prevalent sizes is 95 mm diameter disks. Accordingly, the substrates used to manufacture such disks are about 95 mm (e.g. 95.025 mm) in diameter, and substrate carriers used to manufacture such disks have openings designed to accommodate such substrates.
Recently, smaller disk sizes have been introduced. For example, disks are being designed that are about 27 mm in diameter. Normally, this would require retooling the manufacturing apparatus to accommodate the new substrate sizes. For example, one would have to design and build completely new substrate carriers. Such retooling is expensive and difficult. It would be desirable to be able to accommodate this smaller substrate size with a minimum of effort.
A first substrate carrier in accordance with the invention holds one or more of substrates (e.g. five substrates) during a deposition process (e.g. a sputtering process). In one embodiment, the substrates have a smaller diameter than substrates now prevalent (e.g. smaller than 95 mm).
In one embodiment, the first substrate carrier fits within an opening in a second substrate carrier. The opening of the second carrier is substantially circular, and has a size and shape such that it can accommodate a substrate such as (for example) a 95 mm diameter substrate. The second substrate carrier can be a carrier in accordance with the ""301 application or the above-incorporated Komag patents. The second carrier can also be in accordance with another carrier design. However, during a method in accordance with this invention, instead of simply carrying a substrate, the second carrier carries the first substrate carrier, and the first substrate carrier holds one or more substrates.
In one embodiment, the second carrier comprises one opening for receiving either a substrate or the first carrier. In another embodiment, the second carrier can have more than one opening for receiving either substrates or carriers.
The first and second substrate carriers can be designed for low temperature sputtering processes. Alternatively, the first and second carriers can be designed for high temperature sputtering processes.
In one embodiment, the first and second carriers can be used in conjunction with a sputtering process. In another embodiment, the first and second carriers can be used in conjunction with other kinds of deposition processes, e.g. chemical vapor deposition, plasma-enhanced chemical vapor deposition, cathodic arc deposition or ion beam deposition.
In one embodiment, the substrates are used during magnetic disk manufacturing. Such substrates can be metallic (e.g. an aluminum alloy plated with NiP), glass, glass ceramic or other material. In other embodiments, the substrates are used during other types of manufacturing processes, e.g. integrated circuit manufacturing.
In one embodiment, the carriers are used in conjunction with in-line sputtering apparatus. Alternatively, the carriers can be used in conjunction with static sputtering apparatus.
In static sputtering apparatus, in the prior art, a substrate carrier holds up to two substrates and material is only sputtered onto one substrate at a time. In the present invention, without modifying the original carrier, the sputtering apparatus can now sputter material from a sputtering target onto several substrates simultaneously, e.g. five substrates at a time. Thus, a carrier in accordance with the present invention has the advantage of permitting one to deposit layers on several substrates simultaneously to thereby increase throughput when using such a carrier. In other words, throughput is increased by permitting deposition on more substrates simultaneously than the sputtering apparatus and carrier previously accommodated.